Use black bananas. In fact, if they turn black, put bananas into freezers to keep for when you're ready to prepare. Once defrosted they will be pulp like and mix into cake batter much more easily giving you a cooked consistency like mud cake. Sometimes requires a little extra time in the oven. Don't panic - just keep testing with a tester and take out when ready. Can be iced with a chocolate ganache. Is delicious once cooled but the flavour really kicks in after 24 hours.